Adv550 original sources

The gzipped tarball orig550.tgz 114.6 KB, contains:

    Dave Platt's unmodified A-code source of Adv550, dated 18 Sep 1984.
    My reconstructions of Platt's original F77 munger and executive to handle the A-code source.
    A subdirectory of PL6 sources (as preserved in the IF Archive)
    A separate document explaining what's what, and saying a few words about this package came about.